Aromatic hydrodealkylation process with sulfur oxide containing catalyst

ABSTRACT

A catalyst composition and a process for hydrodealkylating a C 9  + aromatic compound such as, for example, 1,2,4-trimethylbenzene to a C 6  to C 8  aromatic hydrocarbon such as a xylene are disclosed. The composition comprises an alumina, a metal oxide, and a acid site modifier selected from the group consisting of silicon oxides, sulfur oxides, phosphorus oxides, boron oxides, magnesium oxides, tin oxides, titanium oxides, zirconium oxides, molybdenum oxides, germanium oxides, indium oxides, lanthanum oxides, cesium oxides, and combinations of any two or more thereof. The process comprises contacting a fluid which comprises a C 9  + aromatic compound with the catalyst composition under a condition sufficient to effect the conversion of a C 9  + aromatic compound to a C 6  to C 8  aromatic hydrocarbon.

FIELD OF THE INVENTION

This invention relates to a catalyst composition useful for converting aC₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon, a process forproducing the composition, and a process for using the composition in ahydrodealkylation process.

BACKGROUND OF THE INVENTION

It is well known to those skilled in the art that aromatic hydrocarbonsare a class of very important industrial chemicals which find a varietyof uses in petrochemical industry. Recent efforts to convert gasoline tomore valuable petrochemical products have therefore focused on thearomatization of gasoline to aromatic hydrocarbons by catalytic crackingin the presence of a catalyst. The aromatic hydrocarbons produced by thearomatization process include C₆ to C₈ hydrocarbons such as benzene,toluene and xylenes (hereinafter collectively referred to as BTX) whichcan be useful feedstocks for producing various organic compounds andpolymers. However, heavier, less useful aromatic compounds are alsoproduced during the aromatization process. It is, therefore, highlydesirable to convert these compounds to the more useful BTX.

Though a metal oxide-promoted alumina such as Cr/A₂ O₃ has been used ascatalyst in a hydrodealkylation process, the conversion of a C₉ +aromatic compound and the selectivity to BTX are generally not as highas one skilled in the art would desire. It is also well known to oneskilled in the art that alumina is an acidic metal oxide containing acidsites. One of the possible reasons for such low conversion and lowselectivity is probably due to the acidity of an alumina-based catalyst.

Furthermore, a catalyst used in the hydrodealkylation of these heavieraromatic compounds is generally deactivated in a rather short periodbecause of depositions of carbonaceous material such as, for example,coke on the surface of the catalyst.

Accordingly, there is an ever-increasing need to develop a catalyst anda process for converting these heavier and less useful aromaticcompounds to the more valuable BTX hydrocarbons (hereinafter referred toas hydrodealkylation process) and, in the meantime, for suppressing thecoke formation. Such development would also be a significantcontribution to the art and to the economy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a catalyst composition whichcan be used to convert a C₉ + aromatic compound to a C₆ to C₈ aromatichydrocarbon. Also an object of this invention is to provide a processfor producing the catalyst composition. Another object of this inventionis to provide a process which can employ the catalyst composition toconvert C₉ + aromatic compounds to C₆ to C₈ aromatic compounds. Anadvantage of the catalyst composition is that it decreases coke depositsthereon and exhibits high hydrodealkylation activity, satisfactory yieldof xylenes and BTX, and good stability. Other objects and advantageswill becomes more apparent as this invention is more fully disclosedhereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used as a catalyst for converting a C₉ + aromatic compoundto a C₆ to C₈ aromatic hydrocarbon is provided. The composition is ametal oxide-promoted alumina having incorporated therein an acid sitemodifier wherein the metal of the metal oxide is selected from the groupconsisting of chromium, cobalt, molybdenum, nickel, rhodium, palladium,platinum, tungsten, and combinations of any two or more thereof.

According to a second embodiment of the invention, a process forproducing a composition which can be used as catalyst in ahydrodealkylation process is provided. The process comprises, consistsessentially of, or consists of (1) contacting an alumina, which can beoptionally calcined before being contacted, with an acid site modifierprecursor under a condition sufficient to incorporate the acid sitemodifier into the metal alumina to form an acid site-modified aluminawherein the precursor is selected from the group consisting ofphosphorus-containing compounds, sulfur-containing compounds,boron-containing compounds, silicon-containing compounds,magnesium-containing compounds, tin-containing compounds,titanium-containing compounds, zirconium-containing compounds,molybdenum-containing compounds, germanium-containing compounds,indium-containing compounds, lanthanum-containing compounds,cesium-containing compounds, and combinations of any two or morethereof; (2) contacting the acid site-modified alumina with a metalcompound whose metal is selected from the group consisting of chromium,cobalt, molybdenum, nickel, rhodium, palladium, platinum, tungsten, andcombinations of any two or more thereof whereby a modified alumina isformed; and (3) either calcining the modified alumina or contacting themodified alumina with steam under a condition sufficient to effect theconversion of the metal compound to its corresponding metal oxidewherein the amount of the acid site modifier precursor is the amountthat is sufficient to convert the metal compound to its oxide form. Theprocess can also comprise, consist essentially of, or consist of, (1)contacting an alumina with an acid site modifier precursor and a metalcompound under a condition sufficient to incorporate the acid sitemodifier into the metal alumina to form a modified alumina wherein thealumina can be optionally calcined before being contacted; the acid sitemodifier is selected from the group consisting of phosphorus-containingcompounds, sulfur-containing compounds, boron-containing compounds,silicon-containing compounds, magnesium-containing compounds,tin-containing compounds, titanium-containing compounds,zirconium-containing compounds, molybdenum-containing compounds,germanium-containing compounds, indium-containing compounds,lanthanum-containing compounds, cesium-containing compounds, andcombinations of any two or more thereof; and the metal of the metalcompound is selected from the group consisting of chromium, cobalt,molybdenum, nickel, rhodium, palladium, platinum, tungsten, andcombinations of any two or more thereof whereby an acid site-modifiedalumina is formed; and (2) either calcining the acid site-modifiedalumina or contacting the acid site-modified alumina with steam under acondition sufficient to effect the conversion of the metal compound toits corresponding metal oxide wherein the amount of the acid sitemodifier precursor is the amount that is sufficient to convert the metalcompound to its oxide form.

According to a third embodiment of the present invention, a processwhich can be used for converting a C₉ + aromatic compound to a C₆ to C₈aromatic compound is provided which comprises, consists essentially of,or consists of, contacting a fluid which comprises a C₉ + aromaticcompound, optionally in the presence of an insert fluid such as ahydrogen-containing fluid, with a catalyst composition which is the sameas disclosed above in the first embodiment of the invention under acondition effective to convert a C₉ + aromatic compound to an aromatichydrocarbon containing 6 to 8 carbon atoms per molecule.

According to a fourth embodiment of the invention a process which can beused for improving the yield of BTX or xylenes, or both, in ahydrodealkylation of a C₉ + aromatic compound is provided. The processcomprises, consists essentially of, or consists of contacting analumina-containing catalyst composition with a steam. The catalystcomposition can be the same as that disclosed in the first embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the first embodiment of the invention, a composition whichcan be used as catalyst in a hydrodealkylation process for converting aC₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon is provided.The composition can comprise, consist essentially of, or consist of, ametal oxide-promoted alumina having incorporated therein, or impregnatedthereon, a acid site modifier selected from the group consisting ofsilicon oxides, phosphorus oxides, sulfur oxides, boron oxides,magnesium oxides, tin oxides, titanium oxides, zirconium oxides,molybdenum oxides, germanium oxides, indium oxides, lanthanum oxides,cesium oxides, and combinations of any two or more thereof wherein theacid site modifier is present in the composition in a BTXselectivity-improving amount to improve the selectivity to BTX when thecomposition is used in a hydrodealkylation process.

According to the first embodiment of the invention, the weight ratio ofthe acid site modifier to the metal oxide-promoted alumina can be anyratio so long as the ratio can suppress or reduce the formation ordeposition of coke on a an alumina catalyst during the hydrodealkylationprocess for converting of a C₉ + aromatic compound to a C₆ to C₈aromatic hydrocarbon. Generally, the ratio can be in the range of fromabout 0.0001:1 to about 1: 1, preferably about 0.0005:1 to about 1:1,more preferably about 0.001:1 to about 0.8:1 and most preferably from0.005:1 to 0.5:1 for an effective dehydroalkylation conversion and cokereduction or suppression. Alternatively, the acid site modifier can bepresent in the catalyst composition in the range of from about 0.01 toabout 50, preferably about 0.05 to about 50, more preferably about 0.1to about 45, and most preferably 0.5 to 33 grams per 100 grams of thecatalyst composition.

Any metal oxide-promoted alumina which is known to one skilled in theart to be capable of catalyzing a hydrodealkylation of a C₉ + aromaticcompound to a C₆ to C₈ aromatic hydrocarbon can be employed in thepresent invention. The alumina can be α-alumina, β-alumina, γ-alumina,η-alumina, δ-alumina, or combinations of any two or more thereof. Thepresently preferred alumina is a γ-alumina having a surface area in therange of from about 40 to about 300 m² /g, a total pore volume in therange of from about 0.1 to about 1.

Any metal oxide that, when incorporated into an alumina, is capable ofpromoting the hydrodealkylation of a C₉ + aromatic compound to a C₆ toC₈ aromatic hydrocarbon be employed in the invention. Presently, it ispreferred that the metal oxide is selected from the group consisting ofmolybdenum oxides, chromium oxides, cobalt oxides, nickel oxide, rhodiumoxides, palladium oxides, platinum oxides, tungsten oxides, andcombinations of any two or more thereof wherein the oxidation state ofthe metal can be any available oxidation state. For example, in the caseof a molybdenum oxide, the oxidation state of molybdenum can be 2, 3, 4,5, 6, or combinations of any two or more thereof. The presentlypreferred metal oxide-promoted alumina is a Mo/Al₂ O₃ wherein the Mo/Al₂O₃ denotes an alumina promoted with a molybdenum oxide. The presentlymore preferred metal oxide is a molybdenum(VI) oxide. These metaloxide-promoted aluminas are commercially available. However, it ispreferred they be produced by the process disclosed in the secondembodiment of the invention. The weight percent (%) of a metal oxide tothe catalyst composition can be any weight % so long as such weight %can be effective on a hydrodealkylation process. The weight % can be inthe range of from about 0.1% to about 60%, preferably about 0.5 to about50%, and most preferably 1 to 40%. If a combination of metal oxides isemployed, the molar ratio of the second metal oxide, or the third metaloxide, or the fourth metal oxide to the first metal oxide can be in therange of about 0.01:1 to about 100:1.

According to the present invention, any acid site modifier that, ascompared to use of a metal oxide-promoted alumina only, can effect thereduction of coke deposition on the metal oxide-promoted alumina, or theincrease in the yield of BTX or xylenes, or both, during the conversionof a C₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon can beemployed. Presently it is preferred that the acid site modifier isselected from the group consisting of sulfur oxides, silicon oxides,phosphorus oxides, boron oxides magnesium oxides, tin oxides, titaniumoxides, zirconium oxides, molybdenum oxides, germanium oxides, indiumoxides, lanthanum oxides, cesium oxides, and combinations of any two ormore thereof.

Any methods known to one skilled in the art for incorporating a compoundor a portion thereof into an alumina such as, for example, impregnationor extrusion can be employed for producing the composition of thepresent invention. However, it is presently preferred the composition beproduced by the process disclosed in the second embodiment of theinvention.

As disclosed above, the alumina can be α-alumina, β-alumina, γ-alumina,η-alumina, δ-alumina, or combinations of any two or more thereof. Thepresently preferred alumina is γ-alumina having a surface area in therange of from about 40 to about 300 m² /g, a total pore volume in therange of from about 0.1 to about 1. These aluminas are commerciallyavailable.

An alumina is generally first treated with a acid site modifierprecursor. According to the second embodiment of the present invention,any acid site modifier precursor which can be converted to a acid sitemodifier, as disclosed in the first embodiment of the invention, that,as compared to use of a metal oxide-promoted alumina only, can effectthe improvement of selectivity to BTX or xylene or the reduction of cokein a hydrodealkylation process can be employed. Presently it ispreferred that a acid site modifier precursor be selected from the groupconsisting of sulfur-containing compounds, phosphorus-containingcompounds, boron-containing compounds, magnesium-containing compounds,tin-containing compounds, titanium-containing compounds,zirconium-containing compounds, molybdenum-containing compounds,germanium-containing compounds, indium-containing compounds,lanthanum-containing compounds, cesium-containing compounds, andcombinations of any two or more thereof

Generally any silicon-containing compounds which can be converted to asilicon oxide that are effective to enhance hydrodealkylation of a C₉ +aromatic compound when used with a metal oxide-promoted alumina can beused in the present invention. Examples of suitable silicon-containingcompounds can have a formula of (R)(R)(R)Si.paren open-st.O_(m)Si(R)(R).paren close-st.R wherein each R can be the same or differentand is independently selected from the group consisting of alkylradicals, alkenyl radicals, aryl radicals, alkaryl radicals, aralkylradicals, and combinations of any two or more thereof; m is 0 or 1; andn is 1 to about 10 wherein each radical can contain 1 to about 15,preferably 1 to about 10 carbon atoms per radical. Specific examples ofsuch polymers include, but are not limited to, silicon-containingpolymers such as poly(phenylmethylsiloxane), poly(phenylethylsiloxane),poly(phenylpropylsiloxane), hexamethyldisiloxane,decamethyltetrasiloxane, diphenyltetramethyldisiloxane, and combinationsof any two or more thereof. Other silicon-containing compounds includeorganosilicates such as, for example, tetraethyl orthosilicate,tetrabutyl orthosilicate, tetrapropyl orthosilicate, or combination ofany two or more thereof. A number of well known silylating agents suchas trimethylchlorosilane, chloromethyldimethylchlorosilane,N-trimethylsilylimidazole, N,O-bis(trimethylsilyl)acetimide,N-methyl-N-trimethylsilyltrifluoroacetamie,t-butyldimethylsilylimidazole, N-trimethylsilylacetamide,methyltrimethoxysilane, vinyltriethoxysilane, ethyltrimethoxysilane,propyltrimethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, 3-(²-aminoethyl)aminopropyl!trimethoxysilane, cyanoethyltrimethoxysilane,aminopropyltriethoxysilane, phenyltrimethoxysilen, (3-chloropropyl)trimethoxysilane, (3 -mercaptopropyl)trimethoxysilane,(3-glycidoxypropyl)trimethoxysilane, vinyltris(β-methoxyethoxy)silane,(γ-methacryloxypropyl)trimethoxysilane, vinylbenzyl cationic silane,(4-aminopropyl)triethoxysilane,γ-(β-aminoethylamino)propyl!trimethoxysilane,(γ-glycidoxypropyl)trimethoxysilane,β-(3,4-epoxycyclohexyl)ethyl!trimethoxysilane,(β-mercaptoethyl)trimethoxysilane, (γ-chloropropyl)trimethoxysilane, andcombinations of any two or more thereof can also be employed. Thepresently preferred silicon-containing compounds are tetraethylorthosilicate and poly(phenylmethyl) siloxane.

Similarly, any phosphorus-containing compounds that, when impregnatedonto or incorporated into a metal oxide-promoted alumina can beconverted into a phosphorus oxide and are capable of reducing cokedeposition on a metal oxide-promoted alumina, as compared to the use ofthe metal oxide-promoted alumina only, can be used in the presentinvention. Examples of suitable phosphorus-containing compounds include,but are not limited to, phosphorus pentoxide, phosphorus oxychloride,phosphoric acid, phosphines having the formula of P(OR)₃, P(O)(OR)₃,P(O)(R)(R)(R), P(R)(R)(R), and combinations of any two or more thereofwherein R is the same as that disclosed above.

According to the present invention, any sulfur-containing compound thatcan be converted to a sulfur oxide upon calcining can be employed in thepresent invention. Example of suitable sulfur containing compoundsinclude, but are not limited to, (RSH)_(n), RSNR, RS(O)R, RS(O)(O)R,M_(z) S, SX_(z), SO_(z) X_(z), CO_(m) S_(z), M_(z) H_(m) SO₄, orcombinations of any two or more thereof wherein each R, m, and n are thesame as those disclosed above, z is a number that fills the propervalency of M or X in which M is an alkali metal ion, an alkaline earthmetal ion, an ammonium ion, or H, and X is a halogen or hydrogen.Specific examples of sulfur-containing compounds include, but are notlimited to, ammonium sulfide, sodium sulfide, ammonium hydrogen sulfate,sodium hydrogen sulfide, potassium hydrogen sulfide, dimethyl disulfide,methyl mercaptan, diethyl disulfide, dibutyl trisulfide, sulfurylchloride, sulfur monochloride, dinonyl tetrasulfide, hydrogen sulfide,carbon disulfide, carbonyl sulfide, sulfonyl chloride, or combinationsof any two or more thereof.

According to the present invention, any boron-containing compound which,upon being incorporated into a metal oxide-promoted alumina can beconverted into a boron oxide can be used in the present invention.Examples of suitable boron-containing compounds include, but are notlimited to boric acid, borane-ammonium complex, boron trichloride, boronphosphate, boron nitride, triethyl borane, trimethyl borane, tripropylborane, trimethyl borate, triethyl borate, tripropyl borate, trimethylboroxine, triethyl boroxine, tripropyl boroxine, and combinations of anytwo or more thereof.

Examples of suitable magnesium-containing compounds include, but are notlimited to, magnesium formate, magnesium acetate, magnesium bromide,magnesium bromide diethyl etherate, magnesium chloride, magnesiumfluoride, magnesium nitrate, magnesium sulfate, dibutyl magnesium,magnesium methoxide, and combinations of any two or more thereof.

Similarly, examples of suitable tin-containing compound include, but arenot limited to, stannous acetate, stannic acetate, stannous bromide,stannic bromide, stannous chloride, stannic chloride, stannous oxalate,stannous sulfate, stannic sulfate, stannous sulfide, and combinations ofany two or more thereof.

Examples of suitable titanium-containing compounds include, but are notlimited to, titanium zinc titanate, lanthanum titanate, titaniumtetramides, titanium tetramercaptides, titanium tetrabutoxide, titaniumtetramethoxides, titanium tetraethoxide, titanium tetrapropoxide,titanium tetrachloride, titanium trichloride, titanium bromides, andcombinations f any two or more thereof.

Similarly, examples of suitable zirconium-containing compounds include,but are not limited to, zirconium acetate, zirconium formate, zirconiumchloride, zirconium bromide, zirconium butoxide, zirconiumtert-butoxide, zirconium chloride, zirconium citrate, zirconiumethoxide, zirconium methoxide, zirconium propoxide, and combinations ofany two or more thereof.

Suitable molybdenum-containing compounds include, but are not limitedto, molybdenum(III) chloride, molybdenum(II) acetate, molybdenum(IV)chloride, molybdenum(V) chloride, molybdenum(VI) fluoride,molybdenum(VI) oxychloride, molybdenum(IV) sulfide, sodium molybdate,potassium molybdate, ammonium heptamolybdate(VI), ammoniumphosphomolybdate(VI), ammonium dimolybdate(VI), ammoniumtetrathiomolybdate(VI), or combinations of two or more thereof.

Examples of suitable germanium-containing compounds include, but are notlimited to, germanium chloride, germanium bromide, germanium ethoxide,germanium fluoride, germanium iodide, germanium methoxide, andcombinations of any two or more thereof. Examples of suitableindium-containing compounds include, but are not limited to indiumacetate, indium bromide, indium chloride, indium fluoride, indiumiodide, indium nitrate, indium phosphide, indium selenide, indiumsulfate, and combinations of any two or more thereof. Examples ofsuitable lanthanum-containing compounds include, but are not limited to,lanthanum acetate, lanthanum carbonate, lanthanum octanoate, lanthanumfluoride, lanthanum chloride, lanthanum bromide, lanthanum iodide,lanthanum nitrate, lanthanum perchlorate, lanthanum sulfate, lanthanumtitanate, and combinations of any two or more thereof.

An alumina can be optionally calcined before it is used in the secondembodiment of the invention to remove any possible contamination(s) inthe alumina. The condition for calcining an alumina can be any conditionknown to one skilled in the art. The calcining can also be carried outunder the condition disclosed hereinbelow.

Generally, in the first step of the process of the second embodiment ofthe invention, an alumina can be combined with an acid site modifierprecursor in any suitable weight ratios which would result in the weightratios of a acid site modifier to a metal oxide-promoted aluminadisclosed in the first embodiment of the invention. Presently it ispreferred that such combination be carried out in a suitable liquid,preferably an aqueous medium, to form an incipient wetnessalumina-precursor mixture. The combining of an alumina and an acid sitemodifier can be carried out at any temperature. Generally, thetemperature can be in the range of from about 15° C. to about 100° C.,preferably about 20° C. to about 100° C., and most preferably 20° C. to60° C. under any pressure, preferably atmospheric pressure, for anylength so long as the acid site modifier and the alumina are well mixed,generally about 1 minute to about 15 hours, preferably about 1 minute toabout 5 hours.

Upon completion of incorporating the acid site modifier precursor intoan alumina, an acid site-modified alumina is formed. In the next step ofthe process, the acid site-modified aluminum is then contacted,generally mixed, with a metal compound which can be converted, in thenext step of the process, to a metal oxide shown in the first embodimentof the invention. In this step, a modified alumina is produced. Thecontacting can be carried out by the same procedure as disclosed in thefirst step of the second embodiment of the invention. The metal of asuitable metal compound is selected from the group consisting ofchromium, cobalt, molybdenum, nickel, rhodium, palladium, platinum,tungsten, and combinations of any two or more thereof.

The presently preferred process for incorporating an acid site modifierand a metal oxide into an alumina is that the incorporation of the acidsite modifier precursor into the alumina is carried out simultaneously,or contemporaneously with, the incorporation of the metal compound toform a modified alumina. More specifically, an acid site modifier and ametal compound are simultaneously contacted with, or co-impregnatedonto, an alumina. The condition for carrying out this simultaneouscontacting of both an acid site modifier and a metal compound can be thesame as that disclosed above in the first step of the second embodimentof the invention.

Examples of suitable metal compounds include, but are not limited to,molybdenum(II) acetate, ammonium molybdate, ammonium dimolybdate,ammonium heptamolybdate, phosphomolybdate, molybdenum(III) bromide,molybdenum(II) chloride, molybdenum(IV) chloride, molybdenum(V)chloride, molybdenum hexacarbonyl, molybdenum(IV) sulfide, sodiummolybdate, potassium molybdate, molybdenum oxychloride, molybdenumfluoride, molybdenum(VI) tetrachloride oxide, ammoniumtetrathiomolybdate, chromium(II) acetate, chromium(III) acetate,chromium(III) acetylacetonate, chromium(II) chloride, chromium(III)chloride, chromium(II) fluoride, chromium(III) fluoride, chromiumhexacarbonyl, chromium(III) nitrate, chromium nitride, chromium(III)2,4-pentanedionate, chromium(III) perchlorate, chromium(III) potassiumsulfate, chromium(III) sulfate, chromium(III) telluride, cobalt(II)acetate cobalt(II) acetylacetonate, cobalt(III) acetylacetonate,cobalt(II) benzoylacetonate, cobalt(II) bromide, cobalt(II) carbonate,cobalt(II) chloride, cobalt(II) 2-ethylhexanoate, cobalt(II) fluoridecobalt(III) fluoride, cobalt(II) iodide, cobalt(II) iodide, cobalt(II)2,3-naphthalocyanine, cobalt(II) nitrate, cobalt(II) oxalate, cobalt(II)perchlorate, cobalt(II) phthalocyanine, cobalt(II) sulfate, cobalt(II)thiocyanate, cobalt(II) tungstate, nickel(II) acetate, nickel(II)acetylacetonate, nickel(II) bromide, nickel(II) carbonate, nickel(II)chloride, nickel(II) nitrate, nickel(II) perchlorate, nickel phosphide,nickel(II) sulfate, nickel sulfide, nickel(II) titanate, palladium(II)acetate, palladium(II) acetylacetonate, palladium(II) bromide,palladium(II) iodide, palladium(II) nitrate, palladium(II) sulfate,palladium(II) sulfide, rhodium(II) acetate, rhodium(III)acetylacetonate, rhodium(III) bromide, rhodium(III) chloride,rhodium(III) nitrate, rhodium(II) octanoate, rhodium(III) phosphate,rhodium(III) sulfate, tungsten(V) bromide, tungsten(IV) chloride,tungsten(VI) chloride, tungsten hexacarbonyl, tungsten(VI) oxychloride,tungsten(IV) sulfide, tungstic acid, and combinations of any two or morethereof. The presently preferred metal compounds include, but are notlimited to, molybdenum(II) acetate, ammonium molybdate, ammoniumdimolybdate, ammonium heptamolybdate, ammonium tetrathiomolybdate,phosphomolybdate, molybdenum(III) bromide, molybdenum(II) chloride,molybdenum(IV) chloride, molybdenum(V) chloride, molybdenumhexacarbonyl, molybdenum(IV) sulfide, sodium molybdate, potassiummolybdate, molybdenum oxychloride, molybdenum fluoride, molybdenum(VI)tetrachloride oxide, and combinations of any two or more thereof. Thepresently most preferred metal compound is ammonium heptamolybdate forit is readily available and effective.

In the next step, the modified alumina is subject to calcination under acondition that can include a temperature in the range of from about 300°C. to about 1000° C., preferably about 350° C. to about 750° C., andmost preferably 400 ° C. to 650 ° C. under a pressure in the range offrom about 1 to about 10, preferably about 1 atmospheres for a period inthe range of from about 1 to about 30, preferably about 1 to about 20,and most preferably 1 to 15 hours.

Preferably the modified alumina is treated with a steam under a suitablecondition sufficient to effect the conversion of the acid site-modifierprecursor and the metal compound, which have been incorporated into thealumina, to their corresponding oxide form. The modified alumina can beair dried to remove most moisture content before being steam-treated.Air drying can be carried out at a temperature for about 25° C. to about150° C. for about 1 minute to about 30 hours under any pressure such asatmospheric pressure. The air-dried modified alumina can then be treatedwith a steam. Generally the steam temperature can be in the range offrom about 120° C. to about 1500° C., preferably about 200° C. to about1200° C., and most preferably 250° C. to 1000° C. The treatment periodcan be as short as 5 minutes to as long as about 30 hours so long as itis sufficient to convert the acid site modifier precursor and metalcompound to their oxide form. The treatment can be carried out under apressure in the range of from about atmospheric pressure to about 2,000,preferably to about 1,500, and most preferably to 1000 psig.

The composition of the invention then can be, if desired, pretreatedwith a reducing agent before being used in a hydrodealkylation process.The presently preferred reducing agent is a hydrogen-containing fluidwhich comprises molecular hydrogen (H₂) in the range of from 1 to about100, preferably about 5 to about 100, and most preferably 10 to 100volume %. The reduction can be carried out at a temperature, in therange of from about 250° C. to about 800° C. for about 0.1 to about 10hours preferably about 300° C. to about 700° C. for about 0.5 to about 7hours, and most preferably 350° C. to 650° C. for 1 to 5 hours.

According to the third embodiment of the present invention, a processuseful for converting a C₉ + aromatic compound to a C₆ to C₈ aromatichydrocarbon comprises, consists essentially of, or consists ofcontacting a fluid stream comprising a C₉ + aromatic compound and,optionally, in the presence of an inert fluid such as, for example,hydrogen-containing fluid, with a catalyst composition under a conditionsufficient to effect the conversion of a C₉ + aromatic compound to a C₆to C₈ aromatic hydrocarbon. The inert fluid can be hydrogen, nitrogen,helium, argon, carbon dioxide, neon, steam, and combinations of any twoor more thereof. The presently preferred inert fluid is ahydrogen-containing fluid. The inert fluid can also be fed separatelyinto contact with a C₉ + aromatic compound and a catalyst. The catalystcomposition is the same as that disclosed in the first embodiment of theinvention.

The term "fluid" is used herein to denote gas, liquid, vapor, orcombinations of two or more thereof. The term "C₉ + aromatic compound"is referred to, unless otherwise indicated, as a substituted aromaticcompound containing at least 9 carbon atoms per molecule. Preferably thesubstituted aromatic compound has the formula of R'qAr wherein each R'is a hydrocarbyl radical having 1 to about 15 carbon atoms and isindependently selected from the group consisting of alkyl radicals, arylradicals, alkaryl radicals, aralkyl radicals, alkenyl radicals, andcombinations of any two or more thereof, q is a whole number from 1 to5, and Ar is a phenyl group. More preferably R' is an alkyl radicalhaving 1 to about 10 carbon atoms and the aromatic compound has 9 toabout 16 carbon atoms per molecule. Most preferably the aromaticcompound contains 9 to 12 carbon atoms per molecule.

Any fluid which contains a C₉ + aromatic compound as disclosed above canbe used as the feed for the process of this invention. The origin ofthis fluid feed is not critical. However, a preferred fluid feed is aC₉ + aromatic compound derived from the heavies fraction of a productfrom a paraffin, in particular gasoline, aromatization reaction.Generally, this heavies fraction contains primarily trimethylbenzenessuch as 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, and1,3,5-trimethylbenzene and tetramethylbenzenes such as1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene and1,2,4,5-tetramethylbenzene. Additionally, n-propylbenzene,3-ethyltoluene, 4-ethyltoluene, 3-n-propyltoluene, 4-n-propyltoluene,and 1,3-diethylbenzene can also be present in the fluid. Benzene,toluene, ethylbenzene and xylenes are generally substantially absentfrom the fluid, i.e., the amount of each of these aromatic hydrocarbonsis less than about 0.1 weight %. Thus, there is no significantalkylation of these lower aromatic hydrocarbons by the C₉ + aromaticcompound, i.e., no significant transalkylation occurs as a side-reactionin the process of this invention. To demonstrate the process of theinvention, a trimethyl benzene such as 1,2,4-rimethylbenzene was used.

Any hydrogen-containing fluid which comprises, consists essentially of,or consists of, molecular hydrogen (H₂) can be used in the process ofthis invention. This hydrogen-containing fluid can therefore contain H₂in the range of from about 1 to about 100, preferably about 5 to about100, 5 and most preferably 10 to 100 volume %. If the H₂ content in thefluid is less than 100%, the remainder of the fluid may be any inert gassuch as, for example, N₂, He, Ne, Ar, steam, or combinations of any twoor more thereof, or any other fluid which does not significantly affectthe process or the catalyst composition used therein.

The contacting of a fluid containing a C₉ + aromatic compound, in thepresence or absence of a hydrogen-containing fluid, with a catalystcomposition can be carried out in any technically suitable manner, inbatch, semicontinuous, or continuous process under a condition effectiveto convert a C₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon.Generally, a fluid containing a C₉ + aromatic compound, preferably beingin the vaporized state, and a hydrogen-containing fluid are introducedinto a fixed catalyst bed, or a moving catalyst bed, or a fluidizedcatalyst bed, or combinations of any two or more thereof by any meansknown to one skilled in the art such as, for example, pressure, meterpump, and other similar means. The condition can include an hourly spacevelocity (HSV) of the C₉ + aromatic compound fluid stream in the rangeof about 0.01 to about 100, preferably about 0.05 to about 50, and mostpreferably 0.1 to 30 g feed/g catalyst/hour. The hydrogen-containingfluid hourly space velocity generally is in the range of about 1 toabout 10,000, preferably about 5 to about 7,000, and most preferably 10to 5,000 ft³ H₂ /ft³ catalyst/hour. The preferred molar ratio of H₂ tothe C₉ + aromatic compound can be in the range of from about 0.01:1 toabout 20: 1, preferably about 0.1:1 to about 10:1, and most preferably0.5:1 to 5:1. Generally, the pressure can be in the range of from about30 to about 1000 psig, preferably about 50 to about 750 psig, and mostpreferably 200 to 600 psig, and the temperature is about 250 to about1,000° C., preferably about 350 to about 800° C., and most preferably400° C. to 650° C.

The process effluent generally contains a heavies fraction ofunconverted C₉ + aromatics and other heavy (C₉ +) aromatic compoundswhich may have been formed by side-reactions (such as isomerization); alights fraction of alkanes, mainly methane, ethane, propane, n-butane,isobutane, and minor amounts (about 0.1 to about 5 weight %) of C₅ andC₆ alkanes such as, for example, isopentane and n-pentane; and a BTXaromatic hydrocarbons fraction (benzene, toluene, ortho-xylene,meta-xylene and para-xylene). Generally, the effluent can be separatedinto these principal fractions by fractionation distillation which iswell known to one skilled in the art. The heavies fraction can berecycled to a hydrodealkylation reactor described above, the lightsfraction can be used as fuel gas or as a feed for other reactions suchas, for example, in a thermal cracking process to produce ethylene andpropylene, and the BTX fraction can be further separated into individualC₆ to C₈ aromatic hydrocarbon fractions. Alternatively, the BTX fractioncan undergo one or more reactions either before or after separation toindividual C₆ to C₈ hydrocarbons so as to increase the content of themost desired BTX aromatic hydrocarbon. Suitable examples of suchsubsequent C₆ to C₈ aromatic hydrocarbon conversions aredisproportionation of toluene (to form benzene and xylenes) involvingtransalkylation benzene and xylenes (to form toluene), and isomerizationof meta-xylene and/or ortho-xylene to para-xylene.

After the catalyst composition has been deactivated by, for example,coke deposition or feed poisons, to an extent that the feed conversionand/or the selectivity to the most valuable C₆ to C₈ aromatic product(generally xylenes) have become unsatisfactory, the catalyst compositioncan be reactivated by any means known to one skilled in the art such as,for example, calcining in air to bum off deposited coke and othercarbonaceous materials, such as oligomers or polymers, preferably at atemperature of about 400 to about 650° C., followed by a treatment witha reducing agent such as, for example, with hydrogen gas at atemperature of about 400 to about 600° C. The optimal time periods ofthe calcining and treatment with a reducing agent depend generally onthe types and amounts of deactivating deposits on the catalystcomposition and on the calcination and reduction temperatures. Theseoptimal time periods can easily be determined by those possessingordinary skills in the art and are omitted herein for the interest ofbrevity.

According to the fourth embodiment of the invention, a process which canbe used to prepare a catalyst composition is provided. The process cancomprise, consist essentially of, or consist of, contacting analumina-containing catalyst with a steam under a condition that issufficient to effect the improvement of the catalyst activity orselectivity to a desired catalytic product. The alumina-containingcatalyst can be an alumina, or alumina having incorporated therein orimpregnated thereon a modifier, a promoter, or both. The presentlypreferred catalyst is a metal oxide-promoted alumina having incorporatedtherein a modifier. The metal oxide can be the same as that disclosedabove in the previous embodiments of the invention. The modifier can beany modifier so long as it improves the catalyst activity or selectivityto a desired product. The presently preferred modifier is the same asthat disclosed above in the previous embodiments of the invention.

The steam treatment of an alumina-containing catalyst can be carried outunder a condition sufficient to effect the production of a catalyst thathas the characteristics described immediately above. Generally, thecondition can include a temperature in the range of from about 120° C.to 1500° C., preferably about 200° C. to about 1200° C., and mostpreferably 250° C. to 1000° C.; a contacting period in the range of fromabout 5 minutes to about 30 hours, preferably about 20 minutes to about25 hours, and most preferably 1 hour to 20 hours; a pressure in therange of from about 1 atmosphere to about 2,000 psig, preferably toabout 1,500 psig, and most preferably to 1,000 psig.

The following examples are presented to further illustrate thisinvention and are not to be construed as unduly limiting the scope ofthe present invention. The examples illustrate the preparation ofcatalyst compositions of the invention and the use of the composition ina hydrodealkylation process.

A γ-alumina obtained as 1/16 inch extrudates from Criterion CatalystCompany L.P., Michigan City, Ind. was used. First, 10 g of the aluminawas well mixed at 25 ° C. with 5.62 g of 10 weight % (NH₄)₆ Mo₇ O₂₄ ·4H₂O (ammonium heptamolybdate) solution. The resulting mixture was calcinedat 538° C. for 6 hours in a maffle furnace (air) to produce 10.41 g of acalcined molybdenum oxide-promoted alumina or Mo/Al₂ O₃ containing 2.934weight % of molybdenum oxide by calculation (control catalyst A).

Secondly, 10 g of a γ-alumina was well mixed with 6.18 g of a mixturecontaining 10 weight % ammonium heptamolybdate, 40 weight % (NH₄)₂ S,and 50 weight % water followed by calcining at 538° C. for 6 hours inair to produce 10.53 g of sulfur oxide modified, molybdenumoxide-promoted alumina (invention catalyst B) containing 3.189 weight %of molybdenum oxide and 2.209 weight % sulfur oxide by calculation.

Thirdly, 12.11 g of a y-alumina was well mixed with 6.65 g of a 19.6weight % ammonium heptamolybdate solution in a jar at 25° C. followed byair drying at 25° C. to no apparent excess moisture and then treatingthe resulting mixture in a U-tube with a steam at 538° C. for 6 hours toproduce a brown-white calcined product which was not uniform in color.It was therefore further calcined at 538 ° C. for 1 hour to produce15.62 g of a molybdenum oxide-incorporated alumina containing 5.929weight % molybdenum oxide by calculation (invention catalyst C).

In a separate run, 15.32 g of an γ-alumina was well mixed with 7.96grams of a solution (P/Mo solution) containing 9.86 weight % ammonium33474US 32 heptamolybdate, 12.68 weight % phosphoric acid, and 77.46weight % water to form a mixture. The mixture was allowed to stand for10 minutes at 25 ° C. Thereafter, the mixture in a U-tube was heatedwith a steam at 650° C. for 6 hours to produce 15.51 g of phosphorusoxide-modified, molybdenum oxide-promoted alumina (invention catalystD). Catalyst D contained 2.748 weight % molybdenum oxide and 2.069weight % of phosphorus oxide by calculation.

In another separate run 10 grams of γ-alumina was well mixed with 5.29 gof the P/Mo solution followed by calcining at 538° C. for 6 hours toproduce 10.18 g of phosphorus oxide-modified, molybdenum oxide-promotedalumina (invention catalyst E). Catalyst E contained 2.807 weight %molybdenum oxide and 2.096 weight % phosphorus oxide by calculation.

These molybdenum oxide-promoted aluminas were then employed, accordingto the third embodiment of the invention, in a hydrodealkylation processfor converting a C₉ + aromatic compound to BTX. The liquid feed in thehydrodealkylation runs was heavy C₉ + aromatic compounds obtained in agasoline aromatization process in which gasoline was converted into BTXand C₉ + aromatic compounds. The composition of the feed is given inTable I which contained less than 2 ppm S. Not given in Table 33474US Iare numerous components which were in very small quantities and, in someinstances, whose chemical structures were unknown.

                  TABLE I    ______________________________________    Composition of Feed    Feed Component         Weight Percent    ______________________________________    c-Hexene-2             1.104    1-Methyl-3-ethylbenzene                           2.254    1-Methyl-4-ethylbenzene                           1.057    1,3,5-Trimethylbenzene 1.958    1-Methyl-2-ethylbenzene                           1.306    1,2,4-Trimethylbenzene 9.977    1,2,3-Trimethylbenzene 3.060    1-Methyl-3-i-propylbenzene                           0.286    2,3-Dihydroindene      2.845    1,3-Diethylbenzene     1.173    1-Methyl-3-n-propylbenzene                           1.543    1,4-Diethylbenzeneylbenzene                           0.910    1-Methyl-4-n-propylbenzene                           0.328    n-Butylbenzene-ethylbenzene                           2.836    1-Methyl-2-n-propylbenzene                           0.889    1,4,-Dimethyl-2-ethylbenzene                           1.991    s-C5-benzene/1,3-dimethyl-4-ethylbenzene                           2.958    1,2-Dimethyl-4-ethylbenzene                           3.454    1,2-Dimethyl-3-ethylbenzene                           1.007    1,2,4,5-Tetramethylbenzene                           1.936    1,2,3,5-Tetramethylbenzene                           2.695    5-Methylindan          3.004    1-Ethyl-2-n-propylbenzene                           1.592    2-Methylindan          3.040    1,3-Di-i-propylbenzene 1.084    Naphthalene            4.767    2-Methylnaphthalene    3.382    1-Methylnaphthalene    1.184    ______________________________________

A stainless-steel reactor tube (inner diameter 0.75 inch; length 20inches) was filled with a 20 ml bottom layer of Alundum® alumina (inert,low surface area alumina), one of the catalysts (in 1/16 inchextrudates) in the center position 5 ml, and a 20 ml top layer ofAlundum® alumina. The catalysts were pretreated with hydrogen (260ml/minute) at 575 ° C. (starting at 25° C. then ramping at 10° C./min)for one hour. The feed was then introduced into the reactor at a rate of20 milliliters/hour (WHSV=5.1), together with hydrogen gas at a rate of260 ml of H₂ /hours. The reaction temperature was 573 ° C. to 579 ° C.as shown in Table II, and the reaction pressure was 500 psig. Thereactor effluent was cooled and analyzed with an on-line gaschromatograph at intervals of about 1 hour. The results are shown inTable II.

                                      TABLE II    __________________________________________________________________________               Catalyst                   Reaction                         Reactor Effluent (wt %).sup.a          Incorp.               Weight                   Temp                      Time            Conversion    Catalyst          Method.sup.b               (g) (°C.)                      (hr)                         Lights                             BTX                                Xyl                                   C.sub.9 +                                      %.sup.c                                            Coke    __________________________________________________________________________    Control A          IMP  3.55                   573                      6.63                         9.5 16.3                                12.0                                   72.5                                      27.5  4.14          AC    Invention B          Coimp               3.40                   575                      6.65                         8.5 19.2                                13.6                                   70.1                                      29.9  4.09          AC    Invention C          IMP  3.55                   574                      6.47                         11.2                             22.4                                15.4                                   63.9                                      36.1  4.77          STM    Invention D          Coimp               3.50                   579                      6.60                         7.3 41.4                                22.4                                   47.5                                      52.5  3.56          STM    Invention E          Coimp               3.37                   576                      6.45                         6.1 22.2                                15.3                                   69.0                                      31.0  3.79          AC    __________________________________________________________________________     .sup.a The values presented, except conversion, are weight percent. Xyl     denotes the total weight % of all xylenes. The lights fraction included     hydrocarbons shown in the text. The coke was determined at the end of a     7hour run by removing the catalyst from the reactor and determined with a     thermal gravimetric analyzer (TGA), manufactured by TA Instruments, New     Castle, Delaware.     .sup.b Incorporation method:. IMP, incipient wetness impregnation with     impregnating solution; AC, air calcination in a maffle furnace; Coimp,     incipient wetness impregnation with impregnating solution containing a     metal compound and an acid site modifier; STM, steam treatment.     .sup.c The % conversion was calculated as 100%  weight % C.sub.9 +.

The results shown in Table II indicate that the invention catalysts B,D, and E, which were produced by impregnation of alumina simultaneouslywith both ammonium heptamolybdate and either ammonium sulfide orphosphoric acid, significantly improved the yield of BTX and xylenes.The results also show that steam treatment of a molybdenumoxide-promoted alumina catalyst (invention catalyst D) havingincorporated therein a phosphorus oxide further significantly improvedthe yield of BTX and xylenes, as compared to the catalyst produced bycalcining. Table II additionally demonstrates that incorporation ofmolybdenum oxide and either sulfur (catalyst B) or phosphorus (catalystE) improved the yields of both BTX and xylenes over control catalyst A.Table II further demonstrates that steam treatment of molybdenumoxide-promoted catalyst modified with a phosphorus compound (catalyst D)or without modification also improved the yields of BTX and xylenes.

The results shown in the above examples clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe ends and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

That which is claimed:
 1. A process comprising contacting a fluid whichcomprises a C₉ + aromatic compound with a catalyst composition under acondition sufficient to effect the conversion of a C₉ + aromaticcompound to a C₆ to C₈ aromatic hydrocarbon wherein said catalystcomposition comprises a metal 5 oxide-promoted alumina havingincorporated therein a sulfur oxide; the metal of said metal oxide isselected from the group consisting of cobalt, molybdenum, nickel,rhodium, palladium, platinum, chromium, tungsten, and combinations ofany two or more thereof, and the weight % of said metal oxide in saidcatalyst composition is in the range of from about 0.1 to about 60%. 2.A process according to claim 1 wherein said C₉ + aromatic compound hasthe formula of R'qAr wherein each R' is a hydrocarbyl radical having 1to about 15 carbon atoms and is independently selected from the groupconsisting of alkyl radicals, aryl radicals, alkaryl radicals, aralkylradicals, alkenyl radicals, and combinations of any two or more thereof,q is a whole number from 1 to 5, and Ar is a phenyl group.
 3. A processaccording to claim 1 wherein said C₉ + aromatic compound comprises anaromatic hydrocarbon selected from the group consisting of1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,1,2,3,4-tetramethylbenzene, 1,2,3 ,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, n-propylbenzene, 3-ethyltoluene,4-ethyltoluene, 3-n-propyltoluene, 4-n-propyltoluene,1,3-diethylbenzene, and combinations of any two or more thereof.
 4. Aprocess according to claim 1 wherein the weight ratio of said sulfuroxide to said metal oxide-promoted aluminum is in the range of fromabout 0.0001:1 to about 1:1.
 5. A process according to claim 1 whereinthe weight ratio of said sulfur oxide to said metal oxide-promotedaluminum is in the range of from 0.005:1 to 0.5:1.
 6. A processaccording to claim 1 wherein said metal oxide is a molybdenum oxide. 7.A process according to claim 1 wherein the weight % of said metal oxidein said catalyst composition is in the range of from 1 to 40%.
 8. Aprocess according to claim 1 wherein said catalyst composition consistsessentially of an alumina, a metal oxide, and a sulfur oxide whereinthemetal of said metal oxide is selected from the group consisting ofcobalt, molybdenum, nickel, rhodium, palladium, platinum, chromium,tungsten, and combinations of any two or more thereof; the weight % ofsaid sulfur oxide in said composition is in the range of from 0.5 to33%; and the weight % of said metal oxide in said composition is in therange of from about 0.1 to about 60%.
 9. A process according to claim 8wherein said metal oxide is a molybdenum oxide and the weight % of saidmetal oxide in said catalyst composition is in the range of from 0.1 to40%.
 10. A process according to claim 1 wherein said contacting iscarried out in the presence of a hydrogen-containing fluid.
 11. Aprocess according to claim 10 wherein said condition comprises a liquidhourly space velocity of said fluid in the range of about 0.1 to about30 g feed/g catalyst/hour, a gas hourly space velocity of saidhydrogen-containing fluid in the range of about 10 ft³ gas/ft³catalyst/hour to about 5,000 ft³ /ft³ catalyst/hour, a molar ratio ofhydrogen to said C₉ + aromatic compound in the range of about 0.5:1 toabout 5: 1, a pressure in the range of about 50 psig to about 750 psig,and a temperature in the range of about 250° C. to about 1000° C.
 12. Aprocess according to claim 11 wherein said condition comprises apressure of about 200 to about 600 psig and a temperature of about 400°to about 650° C.
 13. A process according to claim 12 wherein said C₉+aromatic compound comprises an aromatic hydrocarbon selected from thegroup consisting of 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene,1,3,5-trimethylbenzene, 1,2,3,4-tetramethylbenzene,1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, n-propylbenzene,3-ethyltoluene, 4-ethyltoluene, 3-n-propyltoluene, 4-n-propyltoluene,1,3-diethylbenzene, and combinations of any two or more thereof.
 14. Ahydrodealkylation process comprising contacting in the presence of ahydrogen containing fluid, a fluid comprising a C₉ + aromatic compoundwith a catalyst composition under a condition sufficient to effect theconversion of said C₉ + aromatic compound to a C₆ to C₈ aromatichydrocarbon wherein said catalyst composition is prepared by the stepscomprising: (1) contacting an alumina with both an acid site modifierprecursor and a metal compound under a condition sufficient toincorporate said acid site modifier precursor into said alumina to forma modified alumina and (2) calcinating said modified alumina under acondition sufficient to effect the conversion of said metal compound toits corresponding metal oxide wherein said acid site modifier is asulfur containing compound and said metal compound whose metal isselected from the group consisting of chromium, cobalt, molybdenum,nickel, rhodium, palladium, platinum, tungsten, and combinations of anytwo or more thereof.
 15. A process according to claim 14, wherein saidacid site modifier precursor further comprises a phosphorous-containingcompound.
 16. A process according to claim 15 whereinsaidsulfur-containing compound is selected from the group consisting of(RSH)_(n), RS_(n) R, RS(O)R, RS(O)(O)R, M_(z) S, SX_(z), SO_(z) X_(z),CO_(m) S_(z), M_(z) H_(m) SO₄, and combinations of any two or morethereof wherein each R has one to about 10 carbon atoms and isindependently selected from the group consisting of an alkyl radical, analkenyl radical, an aryl radical, an aralkyl radical, an alkarylradical, and combinations of any two or more thereof; M is selected fromthe group consisting of hydrogen, an alkali metal ion, an alkaline earthmetal ion, an ammonium ion, and combinations of any two or more thereof;m is 0 or 1; n is 1 to about 10; X is a halogen or hydrogen; and z is anumber filling the necessary valency; and said phosphorus-containingcompound is selected from the group consisting of phosphorus pentoxide,phosphorus oxychloride, phosphoric acid, P(OR)₃, P(O)(OR)₃,P(O)(R)(R)(R), P(R)(R)(R), and combinations of any two or more thereofwherein R has one to about 10 carbon atoms and is independently selectedfrom the group consisting of an alkyl radical, an alkenyl radical, anaryl radical, an aralkyl radical, an alkaryl radical, and combinationsof any two or more thereof.
 17. A process according to claim 14 whereinsaid sulfur-containing compound is selected from the group consisting ofammonium sulfide, sodium sulfide, ammonium hydrogen sulfate, sodiumhydrogen sulfide, potassium hydrogen sulfide, dimethyl disulfide, methylmercaptan, diethyl disulfide, dibutyl trisulfide, sulfuryl chloride,sulfur monochloride, dinonyl tetrasulfide, hydrogen sulfide, carbondisulfide, carbonyl sulfide, sulfonyl chloride, and combination of anytwo or more thereof.
 18. A process according to claim 14 wherein saidmetal compound is a molybdenum-containing compound.
 19. A processaccording to claim 14 wherein said metal compound is ammoniumheptamolybdate.
 20. A process according to claim 18 wherein said acidsite modifier precursor comprises ammonium sulfide and phosphoric acid.21. A process according to claim 18 wherein said acid site modifierprecursor is ammonium sulfide.
 22. A process for converting a C₉ +aromatic compound to a C₆ to C₈ aromatic hydrocarbon comprisingcontacting said C₉ + aromatic compound, in the presence of a catalyst,with a hydrogen-containing fluid wherein said C₉ +aromatic compound hasthe formula of R'qAr wherein each R' is a hydrocarbyl radical having 1to about 15 carbon atoms and is independently selected from the groupconsisting of alkyl radicals, aryl radicals, alkaryl radicals, aralkylradicals, alkenyl radicals, and combinations of any two or more thereof,q is a whole number from 1 to 5, and Ar is a phenyl group; and saidcatalyst comprises a molybdenum oxide-promoted alumina havingincorporated therein an acid site modifier comprising a sulfur oxide.23. A process according to claim 22 wherein said acid site modifierfurther comprises a phosphorus oxide.
 24. A process according to claim1, wherein said metal oxide-promoted alumina has a phosphorous oxidefurther incorporated herein.